ISO/TR 14672:2000
(Main)Graphic technology — Statistics of the natural SCID images defined in ISO 12640
Graphic technology — Statistics of the natural SCID images defined in ISO 12640
This Technical Report provides the colour and spatial frequency distribution statistics associated with the digital image data of International Standard 12640, Graphic technology — Prepress digital data exchange — CMYK standard colour image data (CMYK/SCID).
Technologie graphique — Statistiques des données d'images en couleur normales (SCID) définies dans l'ISO 12640
General Information
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 14672
First edition
2000-07-15
Graphic technology — Statistics of the
natural SCID images defined in ISO 12640
Technologie graphique — Statistique des données d'images en couleur
normales (SCID) définies dans l'ISO 12640
Reference number
©
ISO 2000
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2000 – All rights reserved
©ISO ISO/TR 14672:2000(E)
Contents Page
Foreword . . . iv
Introduction . v
1 Scope .1
2 Reference . 1
3 SCID image description .1
4 Colour distribution .3
4.1 Data value histograms and related things . 3
4.2 Average colour values .5
4.3 4 x 4 covariance matrix .5
4.4 Three-dimensional volumes .6
5 Spatial frequency characteristics .7
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member
bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member
body interested in a subject for which a technical committee has been established has the right to be represented on that
committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical
standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the
technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval
by at least 75 % of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that which is normally
published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its
participating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have
to be reviewed until the data it provides are considered to be no longer valid or useful.
Attention is drawn to the possibility that some of the elements of this Technical Report may be the subject of patent rights.
ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TR 14672 was prepared by Technical Committee ISO TC 130, Graphic technology, Working Group 2, Prepress data
exchange.
iv
©ISO ISO/TR 14672:2000(E)
Introduction
International Standard 12640, Graphic technology — Prepress digital data exchange — CMYK standard colour image data
(CMYK/SCID), provides the digital data for a set of natural and synthetic colour images. The natural images
are intended for use in subjectively evaluating image quality as a function of image processing and/or output process. In
addition, the synthetic images are provided to allow objective measurement of process control, tone reproduction, colour
characterization, etc.
In addition, these images may be used for the statistical evaluation of the change in image content as a function of image
processing or other imaging steps. TC 130 Working Group 2 agreed to provide a set of reference statistics for these images as
a baseline for the technical community wishing to use the images for such statistical evaluation.
This statistical data was prepared by the TC 130 Japanese National Committee, and their efforts have made this technical report
possible.
v
�
TECHNICAL REPORT ISO ISO/TR 14672:2000(E)
Graphic technology —
Statistics of the natural SCID images defined in ISO 12640
1 Scope
This Technical Report provides the colour and spatial frequency distribution statistics associated with the digital image data of
International Standard 12640, Graphic technology — Prepress digital data exchange — CMYK standard colour image data
(CMYK/SCID).
2 Reference
ISO 12640:1997, Graphic technology — Prepress digital data exchange — CMYK standard colour image data (CMYK/SCID).
3 SCID image description
ISO 12640 defines a set of natural and synthetic colour images, called SCID (Standard Colour Image Data), which can be used
for evaluation of image processing algorithms or output devices, and also for colour characterization of output devices.
These images are digital files, encoded in a CMYK format. They exist in two forms, known as the primary and alternate data
sets, each of which has different resolutions and data ranges. The primary data set was created using the data encoding scheme
typical of a Colour Electronic Prepress System (CEPS). The alternate data set was created from the primary data set by re-
encoding the data in the scheme more typically used by the desktop publishing (DTP) prepress systems and defined in ISO 12639
as the P1 profile. With the primary set, tone value of 0% is encoded as data value of 28 and tone value of 100% is encoded as
data value of 228; the corresponding data values for the alternate set are 0 to 255. The primary set has an assumed resolution
of 16 pixels/mm while the alternate set has an assumed resolution of 12 pixels/mm. The alternate set was computed from the
primary set by cubic interpolation combined with a linear mapping of the data values.
The eight natural colour images of the primary set are shown as N1 to N8 in figure 1, the natural colour images of the alternate
set are denoted as N1A to N8A. When output at the assumed resolutions of 16 pixels/mm (406.4 pixels/inch) and 12 pixels/mm
(304.8 pixels/inch) the resultant size is 160mm x 128mm. The primary set of natural images are 2560 x 2048 pixels and the
alternate set are 1920 x 1536 pixels. Table 1 shows the characteristics and typical usage of the images.
These eight images were selected so that users can subjectively evaluate several aspects of image quality that are often reduced
by image processing or as a result of output device characteristics. The image quality attributes in question are described in table
1, but may be summarized as follows:
– colour reproduction;
– sharpness;
– graininess.
Although there is no established procedure for quantitative evaluation of these subjective image quality attributes, by the use
of a common set of images SCID makes it possible to conduct such subjective evaluation on a consistent basis. However, when
evaluating the application of image processing algorithms to the images some quantitative analysis is feasible and in this context
various statistical characteristics calculated from the images may prove useful. Statistics on colour and spatial frequency
distribution are such basic characteristics.
N1 and N1A N2 and N2A
N3 and N3A N4 and N4A
N5 and N5A N6 and N6A
N7 and N7A N8 and N8A
Figure 1 — Reduced monochrome reproductions of the natural images
©ISO ISO/TR 14672:2000(E)
Table 1 — Natural images
Name Aspect Characteristics
N1, Portrait Portrait Used to evaluate the reproduction of human skin.
N2, Cafeteria Portrait Image with complicated geometric shapes. Suitable for evaluating the
result of image processing.
N3, Fruit Basket Landscape Image of a basket and cloth used to evaluate the reproduction of brown
colours and close texture.
N4, Wine and Landscape Image of glassware and silverware used to evaluate the reproduction
Tableware characteristics of highlight tones and neutral colours.
N5, Bicycle Portrait Image of a (penny-farthing) bicycle, resolution charts and other items
containing high detail used to evaluate the sharpness of reproduction and
the results of image processing.
N6, Orchid Landscape Image of an orchid with background vignettes used to evaluate
reproduction of highlight and shadow vignettes.
N7, Musicians Landscape Image of three girls with different skin characteristics and fine detail used
to evaluate the reproduction of different skin tones and image detail.
N8, Candle Landscape “Low-key” image of a room scene containing miscellaneous objects used
to evaluate dark colours, particularly browns and greens.
These characteristics can be used for the comparison between the data of an original image and that of a transformed or degraded
image passing through some image handling system such as an image transmission line, an imaging system, an image storage
system or an image transform and processing system. It is also possible to compute those basic quantities from a set of images
to certify validity of them if this is in doubt.
Members of the technical committee ISO TC 130 evaluated the aforesaid basic statistical quantities for the eight natural SCID
images (for both the primary and alternate set). This technical report summarizes the quantitative results.
4 Colour distribution
Statistics which represent image colour distribution are provided in this section. These were obtained by computing single
dimensional histograms, average colour values of each colour, the three-dimensional volume and covariance matrix and resultant
orthogonal matrix and principal axes. Such data were calculated for each image. The histogram data is provided graphically
(figures 5-12) and numerically (tables 5-12). The remaining statistics are provided in tables 13-20.
It should be noted that each natural image is provided with a text insert such as ISO300 or ISO400 in the image. Pixels
representing this text have a coded value of either 0 (white) or 255 (black). This text serves to distinguish between the primary
set and alternate set. It is not meaningful to include this text in the colour distribution calculation. Therefore, the calculation
was carried out only for the image area, excluding the text.
The position of the outer boundaries of the text is defined by a rectangle produced from the coordinates of two of the corners
as shown in figure 2. The position (in terms of number of pixels) of the text in each image is given in table 2 and table 3. This
was the area excluded prior to calculation of the statistical data but extended by 4 pixels in each direction to minimize any effects
arising from evaluation of the statistics after any image processing which requires calculation based on adjacent pixels. Thus
the coordinates of the corners defining the rectangle enclosing the excluded area are A(X -4,Y -4) and B(X +4,Y +4).
1 1 2 2
4.1 Data value histograms and related things
The histograms for the natural images are shown in figures 5-12. These show the frequency of occurrence of each of the dot
percent equivalent values within the image; therefore, there are four histograms for each image, one for each of the colours cyan,
magenta, yellow and black. Each of the figures has two parts; the first shows the histograms for the primary set of images and
the second part the histograms for the alternate set. The numeric data used to produce these figures are given in tables 5-12.
Figure 2 — Definition of the coordinates of the text elements
Table 2 — Position and area of the text for the primary
set of natural images (16 pixels/mm )
Image A(x ,y ) B(x ,y )
1 1 2 2
N1 (1769,39) (2008,88)
N2 (37,35) (276,84)
N3 (38,36) (277,85)
N4 (41,37) (280,86)
N5 (37,34) (276,83)
N6 (37,35) (276,84)
N7 (2286,35) (2525,84)
N8 (2070,193) (2309,242)
Table 3 — Position and area of the text for the
alternate set of natural images (12 pixels/mm )
Image A(x ,y ) B(x ,y )
1 1 2 2
N1A (1326,24) (1503,61)
N2A (26,23) (203,60)
N3A (25,22) (202,59)
N4A (31,28) (208,65)
N5A (25,23) (202,60)
N6A (25,23) (202,60)
N7A (1708,21) (1885,58)
N8A (1554,145) (1731,182)
It should be noted that although the primary set of images contains data in the ranges 0-27 and 229-255, these are not normally
differentiated by the output device since the values less than or equal to 28 are all set to 0% dot and those greater than or equal
to 228 are all set to 100% dot. In the case of the alternate set, however, all values in the range may be differentiated. This means
that when the alternate set was derived from the primary set all the values in the ranges 0-28 and 229-255 for the primary set
were mapped to 0 and 255 respectively. Thus the histograms for the alternate set tend to show very high frequencies for these
values when compared
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.